I completely sympathize!!! DS is also 16 months and has become fairly physically aggressive. Like yours, it's when he's frustrated about not getting something he wants or me/DH not doing something he wants. He frequently throws things (his blankie, whatever he's eating, the toy he's playing with), so we've worked out a system where he can throw anything he wants in the kitchen and a few specific items (felt cutouts) in any other part of the house. That helps a lot.
However, he has progressed to kicking and hitting, too. I've taken a few non-negotiable steps. First, if I see it coming (which you can with the throwing and hitting), I remind him not to. Then I get very close to him and try to figure out what's going on. "Are you done? Do you need help?" I start basic and try to work to the specific. When I figure it out, I always try to say something to acknowledge what's going on. "I know that you want to sit in my lap right now, but I'm washing the dishes," and give him an alternative, "Why don't you go get a ball and throw it in the kitchen while I finish. I'll be done very soon and then you can sit with me." It seems to help a lot. Also, DH always offers up his lap (or whatever) if possible. I also remind him that he can ask for help if he needs it, "Sebastian, you don't hit. You say 'help,' ok?" He responds fairly well to this because he can say and sign "help."
If he continues the behaviour (kicking during diaper changes is the WORST), he gets one chance. So if he kicks or hits we tell him, "You don't hit people. It hurts. You can't be around people when you hit." Then if he does it again, I immediately put him in his crib for about 1 min and leave the room. When I go back and get him I kiss and cuddle and quietly explain again that hitting hurts and he can't be around people when he behaves that way. Then I say something along the lines of "You can come and join us now. Please be gentle with people."
This was my sister's suggestion based on her experience when her son went through this. She said he learned very quickly that he would be removed from the family's presence with that kind of behaviour. We just started this about a week ago and the grandparents are in town just now, so I don't know how much it's working yet.
You mentioned language as a barrier and I completely agree. If you haven't tried it, you might want to introduce a few basic signs. "More," "Help," "Hungry" and "All Done" work wonders. I found Sign with Your Baby
by Joseph Garcia to be fabulous.
Good luck and keep me posted. I'd love to hear more about what you're trying. "Trying" is certainly the right word, isn't it??? Grrrr.